Similar likelihood of adverse effects with mRNA and inactivated virus vaccines for COVID-19

Reference

Wong CKH, Lau KTK, Xiong X, et al. Adverse events of special interest and mortality following vaccination with mRNA (BNT162b2) and inactivated (CoronaVac) SARS-CoV-2 vaccines in Hong Kong: A retrospective study. PLoS Med 2022;19(6):e1004018.

Synopsis

This retrospective review of safety data included more than 2 million adults who received a first dose and slightly fewer patients who received a second dose of either an mRNA vaccine (Pfizer-BioNTech BNT162b2) or an inactivated whole virus vaccine (CoronaVac). Patients in Hong Kong, where this study was performed, were free to select either vaccine for the first dose but received the same vaccine for the second dose. Using a central database that tracked all recipients, the authors tracked adverse events through hospital records (that is, not via patient self-report). Within the 21 days following vaccination, there were 65 adverse events and 3 deaths in people who received the first dose of the mRNA vaccine, which translates to one event in every 20,137 people and 1 death in every 437,000 people receiving it (these were deaths due to any cause over the 3 weeks), and there were 90 adverse events and 6 deaths in people who received the first dose of the inactivate whole virus vaccine, which translates to approximately one event in every 10,620 people and one death in every 159,000 people receiving it. Following 2 doses, the cumulative incidence of adverse events was 1 in 1523 (0.066%) for the mRNA vaccine and 1 in 1141 (0.088%) for the inactivated vaccine. These rates were not statistically different. Thromboembolic disorders were the most common adverse effect during the time of surveillance, including coronary artery disease, myocardial infarction, or venous or arterial thromboembolism, though the rates could not be compared with the background rate (i.e., rates over the same period among people who did not receive the vaccines).